This disclosure generally relates to systems and methods for measuring a level of liquid in a reservoir, such as a storage tank or other container. More particularly, this disclosure relates to systems and methods for liquid level measurement using an optical sensor.
A need to continuously measure the level of a liquid exists in many commercial and military applications. For example, liquid-level sensors are commonly used in the fuel tanks of airplane, automobiles, and trucks. Liquid-level sensors are also used to monitor liquid levels within storage tanks used for fuel dispensing, wastewater treatment, chemical storage, food processing, etc.
Many transducers for measuring liquid level employ electricity. The electrical output of such transducers changes in response to a change in the liquid level being measured, and is typically in the form of a change in resistance, capacitance, current flow, magnetic field, frequency, and so on. These types of transducers may include variable capacitors or resistors, optical components, Hall Effect sensors, strain gauges, ultrasonic devices, and so on.
Currently most fuel sensors on airplane use electricity. For example, existing electrical capacitance sensors require metallic capacitance plates and metal wiring to be placed inside the tank, which in turn requires complex installations and protection measures to preclude a safety issue under certain electrical fault conditions. This electrical wiring requires careful shielding, bonding, and grounding to minimize stray capacitance and further requires periodic maintenance to ensure electrical contact integrity. Secondly, capacitance probe measurement requires other sensor inputs, such as temperature and density sensor inputs, to supplement the capacitance measurement to accomplish the fuel level sensing.
There is room for improvements in systems and methods that can detect the level of liquid in a fuel tank without introducing electrical current into the fuel tank.